The Draft Standard for OFDMA mobile communication standard enacted by IEEE 802.20, that is, IEEE P802.20/D2.1 Draft Standard for Local and Metropolitan Area Networks—Standard Air Interface for Mobile Broadband Wireless Access Systems Supporting Vehicular Mobility—Physical and Media Access Control Layer Specification, defines an uplink feedback channel that allows a mobile terminal to transmit feedback information to a base station in an uplink.
According to the Draft Standard, a mobile terminal cyclically transmits feedback information to a base station through an uplink feedback channel. The mobile terminal feeds back channel quality information, feedback information for multi-antenna transmission, and base station selection information to the base station on the basis of the feedback information. Then, the base station performs packet scheduling, adaptive modulation and coding scheme setting, antenna weighted value setting for multi-antenna transmission, and high-speed hand-off.
In the Draft Standard of IEEE 802.20, one mobile terminal multiplexes a plurality of feedback information sets using different scrambling codes and transmits the multiplexed feedback information through the feedback channel. At this time, a plurality of mobile terminals multiplex individual multiplexed feedback information sets using different scrambling codes and transmit the multiplexed feedback information through the same feedback channel.
Accordingly, a plurality of mobile terminals use the same wireless resource at the same transmission rate regardless of the channel conditions, which causes deterioration of efficiency of the wireless resource for the feedback channel.
Further, when transmitting various types of feedback information, the mobile terminal transmits the feedback information with the same processing gain and transmission power, and thus importance of individual feedback information is not distinguished.
In addition, since a cyclical feedback channel is allocated to feedback information that is intermittently fed back, the feedback channel is wastefully used.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.